Absorbent Product

ABSTRACT

Absorbent product, such as a diaper, a sanitary napkin or an incontinence product, having a longitudinal and a lateral direction, including a back sheet, being distal from the body of the wearer in use of the product, and a top sheet, being proximal to the body of the wearer in use of the product, the product having a front part, a rear part and a crotch part lying between the front and rear parts, the product further including an absorbent structure, between the top and back sheet, extending longitudinally from the front part to the rear part, and whereby the product includes at least one starch-based odour control agent having a specific area of at least 5 m 2 /g, preferably at least 10 m 2 /g, more preferably at least 50 m 2 /g, even more preferably at least 100 m 2 /g, and most preferably at least 200 m 2 /g. Hereby, an enhanced capacity to absorb malodorous compounds of large size intervals in wet and dry systems is achieved.

TECHNICAL FIELD

This disclosure is in the field of absorbent products, such as diapers,sanitary napkins or incontinence products comprising starch-based odourcontrol agent(s). Further this disclosure refers to the use of astarch-based odour control agent for controlling odour in an absorbentproduct.

TECHNICAL BACKGROUND

Odour control has become an increasingly important feature of absorbentproducts. Bad smells arising from secretions from the wearer of anabsorbent product, or from the storing of bodily fluids within theabsorbent product, give easily rise to bad odours which reduces thecomfort of the wearer. Thus, it is of high importance that odours can belimited or completely prevented in absorbent products during use.

For prevention of odours one is normally focused on either (1)preventing odours from arising, or (2) preventing odours from escapingout of the absorbent product to the surrounding environment. Severaldifferent kinds of odour control agents are known for these purposes.

For instance, for masking odours, fragrances are normally used. Foradsorption of odour substances, zeolites, silica, clays, active carbonand/or cyclodextrin amongst others can be used. Some of these tendhowever to be moisture sensitive. For neutralization of odours, bakingsoda, citric acid and/or acidic SAP can be used. For inhibition ofbacteria growth, copper acetate, SAP with silver and/or acidic SAP canbe used. Accordingly, different kinds of odour control agents areeffective against different kinds of odour substances, and act withdifferent mechanisms.

As an example EP-A-811389 discloses an absorbent article comprising anodour control system that can be chosen from e.g. silica, zeolite,absorbent gelling material, activated carbon, cyclodextrin and mixturesthereof. The odour control system may be layered on the absorbent coreor be mixed within the core. Further, it can be distributed on the edgesof the absorbent article.

A common problem with odour control agents is that they tend to bemoisture sensitive. For instance, this is the case with zeolites andsilica. Accordingly, since absorbent products absorb liquids, it isimportant that the parts of the absorbent products that become wet stillcan be effective in controlling odours.

From U.S. Pat. No. 6,147,028 it is known with an odour control agent inthe form of polysiloxane-coated starch granules that is used in asanitary napkin. Polysiloxane is considered to be the active ingredientsince it provides a hydrophobic surface.

Further, US2005/0108828 discloses the use of native amylose (a fractionof starch) for odour control of e.g. tobacco or sweat in textiles.Absorbent products are not mentioned in the context of this disclosure.Further, from U.S. Pat. No. 3,622,460 it is known that starch-containingcompounds have flavour-retaining properties.

Also, organic volatile substances are important to control in absorbentproducts, since they have undesired odours.

Moreover, U.S. Pat. No. 5,714,445 discloses articles, such as absorbentarticles, comprising small-particle size cyclodextrin (a starch-basedcompound) for odour control. Cyclodextrin is a cyclic molecule that iscomposed of 1,4-alpha-linked glucose units. Cyclodextrin can be built upof 6, 7 or 8 glucose units. The inner diameter (the cavity) ofcyclodextrin depends on the number of glucose units. This cavity ishydrophobic and form complexes with other substances depending on thesize and hydrophobicity of the substance. Also, it will only be capableto take care of complexes when wet. The specific surface area ofcyclodextrin is less than 1 m²/g.

Thus, odour control agents for absorbent products need several featuresto be effective. Moisture-insensitivity to a certain extent, capacity toinhibit various kinds and sizes of odour compounds, not the leasthydrophobic compounds, inexpensiveness, capacity to take care ofmalodours and environmental friendliness are some needs that should bemet.

OBJECTS AND SUMMARY

Accordingly, it is an object of the disclosure to provide an absorbentproduct comprising at least one odour control agent that meets thesedemands and solves the problems as presented above.

The inventors of the present invention have discovered that a physicallyor physicochemically modified starch-based odour control agent having(1) an enhanced specific area of at least 5 m²/g, and/or (2) wherein thestarch-based odour control agent has the ability to form complexes inwater, can be used in an absorbent product, and thereby a beneficialeffect compared to the prior art is achieved, not the least with regardto the effectiveness of the odour control agent. The capacity to bindmalodorous compounds of a large size interval is enhanced compared tothe prior art.

Thus, the disclosure is directed to an absorbent product such as adiaper, a sanitary napkin or an incontinence product, having alongitudinal and a lateral direction, comprising a back sheet, beingdistal from the body of the wearer in use of the product, aid a topsheet, being proximal to the body of the wearer in use of the product,said product having a front part, a rear part and a crotch part lyingbetween the front and rear parts, the product further comprising anabsorbent structure, between the top and back sheet, extendinglongitudinally from the fiont part to the rear part, and whereby theproduct comprises at least one starch-based odour control agent,characterised in that the starch-based odour control agent has aspecific area of at least 5 m²/g, preferably at least 10 m²/g, morepreferably at least 50 m²/g, even more preferably at least 100 m²/g, andmost preferably at least 200 m²/g. Hereby, a very effectiveodour-control for a dry state is obtained. The ability to adsorb e.g.vapours is very high.

Preferably, the starch-based odour control agent has been physically orphysicochemically modified in order to obtain an enhanced specific area.The physico-chemical treatment essentially consists of a process (whichdiffer from material to material) leading to an enlarged surface area,followed by dewatering and fixation. For example, especially foractivated starch, the physicochemical modification comprises the stepsof: (a) swelling the starch-based odour control agent material in water,and (b) dewatering the material of step (a), in order to obtain astarch-based odour control agent having an enhanced specific area.Especially for amylose, the physicochemical modification comprises thestep of precipitating the starch-based odour control agent from solutionwith a complex forming agent. Especially for linear dextrin, thephysicochemical modification comprises the step precipitating thestarch-based odour control agent, either spontaneously or in thepresence of a complex forming agent.

In a preferred embodiment, the starch-based odour control agent has theability to form complexes in water, thereby being effective also in awet state, i.e. when the active sites of the odour control agent havebeen inactivated or have come in contact with water.

In another preferred embodiment the starch-based odour control agent iseffective in both wet and dry conditions.

In a preferred embodiment the starch-based odour control agent is chosenfrom amylose, preferably V-amylose, activated starch and linear dextrin.For example, V-amylose has a specific area of 20-200 m2/g and functionspractically moisture-insensitive. By activating starch an enhancedsurface area is achieved. Also, an enhanced surface area can be obtainedfor linear dextrin. Hereby, suitable for a dry system, a starch-basedodour-control agent having a specific area of at least 10 m2/g,preferably 50 m2/g, more preferably 100 m2/g, and most preferably 200m2/g is achieved.

Further, suitable for a wet system, V-amylose comprises a hydrophobicinner side in its helical structure, which further improves its capacityto adsorb hydrophobic substances. Moreover, linear dextrin is composedof a helical structure (as V-amylose) and thus has the capacity to bindhydrophobic compounds in a similar way.

In yet another preferred embodiment activated starch and/or lineardextrin and/or amylose, especially V-amylose, is positioned mainly inthe dry parts of the product, thereby taking advantage of the highspecific areas of these agents.

In still another preferred embodiment activated starch and/or amylose,especially V-amylose, and/or linear dextrin is positioned at positionsof the product, where air mainly tend to be pressed out of the product.Hereby the agents are positioned at positions where they have a highability to be effective, and to come in contact with malodorous gases.

In still another preferred embodiment, linear dextrin and/or amylose,especially V-amylose, is positioned mainly in the wet parts of theproduct, or in the wet and dry parts of the product, thereby takingadvantage of the complex-forming properties and the high specific areasof these agents.

In yet another preferred embodiment, a combination of amylose,especially V-amylose, activated starch and/or linear dextrin is used.

Also, in still another preferred embodiment, further odour controlagents can be used, e.g. chosen from the group of acidic SAP,cyclodextrin, activated carbon, silica and/or zeolites.

In yet another preferred embodiment the odour control agent ispositioned on the top sheet and/or is positioned directly under the topsheet, and/or is positioned in the absorbent core of the product, and/oris positioned in the edges of the product, and/or is applied within thetop sheet and/or is applied within or on the backing sheet of theproduct, or any other layer of the product.

In another aspect the disclosure relates to the use of a starch-basedodour control agent having a specific area of at least 5 m²/g,preferably at least 10 m²/g, more preferably at least 50 m²/g, even morepreferably at least 100 m²/g, and most preferably at least 200 m²/g forodour control in an absorbent article. Preferably, the starch-basedodour control agent is chosen from at least one of amylose, preferablyV-amylose, activated starch and linear dextrin.

DEFINITIONS

By a “starch-based odour control agent” is meant an odour control agentcomprising, at least partly, a substance that has been derived fromstarch, such as natural starch, starch that has been activated, starchthat has been fractionated or starch that has been modified in any way.

By a “physically or physicochemically modified” starch based odourcontrol agent is meant a starch-based odour control agent that has beentreated by way of physical or physicochemical means so that e.g.enhanced odour control properties in the form of enhanced specific areahas been incurred.

By “activated starch” is meant starch granules which after swelling ortreatment with suitable salts or water-miscible organic solvents have anenlarged surface area and/or enhanced adsorption properties.

By “the dry parts” and “the wet parts” of the absorbent product aremeant the parts of the product that are intended to be kept dry duringuse (dry parts) or to absorb and/or transport liquid during use (wetparts). Hence, dry or wet conditions will mainly be present in theserespective parts after liquid absorption during use.

By “specific area” or “specific surface” is meant the area (of thesubstance that the specific area refers to) that is available forbinding of and/or interaction with other substances, or in other words:the total surface area of the particles in a gram of a substance. Formeasuring specific surface area, the BET-method is used. The BET-theorydescribes the adsorption of nitrogen molecules to a solid surface and isbased upon an assumption for the energy for the adsorption of the firstlayer. By measuring the volume of the nitrogen gas after desorption thespecific surface area is calculated. The method has been developed byBrunauer, Emmett and Teller (BET). The skilled person would knowconventional instruments for performing the measurement. Alternatively,when calculating the geometrical surface area of e.g. corn starch, thedimensions and properties of corn starch (e.g. specific mass of cornstarch=1500 kg/m³; mass media diameter=19-20 μm; volume of asphere=4πR³/3; surface of a sphere is 4πR²) when it is considered as asolid sphere should be considered; i.e. 1 g starch would comprise Nparticles that can be considered as a (hard) sphere.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Starch is stored in plants as a semi-crystalline granule composed of ahighly ordered polymer of glucose. In most cases it is a mixture of 25%amylose and 75% amylopectin. Amylose is linear α-1,4-glucan with a fewbranch points, whilst amylopectin is a highly branched chain of α-1,4-and a α-1,6-glucan chains Starch (and amylose) can e.g. be obtained fromplants such as Acorn, Apple, Arrowroot, Banana, Barley, waxy Barley,Easter lily, Elm, sapwood, Iris tuber, Corn (Zea mays), Corn of hybridamylomaize Class V, Corn of hybrid amylomaize Class VII, Corn of hybridwaxy maize, Oat, Smooth Pea, Wrinkled Pea, Manioc, Parsnip, Potato,Rice, Waxy rice, Sago, Waxy Sorghum, Sweet potato, Tapioca and Wheat(see table 1, “Starch, Chemistry and Technology” (second edition) Ed.Whistler, BeMiller, Paschall, 1984, Chapter 8, Fractionation of starchby Austin H. Young (page 251) for further details). Corn, Wheat andPotato are the preferred starch sources.

Thus, starch consists of two fractions amylose/amylopectin. The ratiodiffers from source to source and variety to variety. The best examplescan be found in the most widely cultured starch source, maize (corn). Inthe waxy variety the ratio amylopectin/amylose is 99:1. In the normalvariety the ratio is 75:25 and in the high amylose variety the ratio is25:75. Waxy varieties are among others also known for potato and rice.These starches consist also of amylopectin.

Of the two components of starch, amylose and amylopectin, amylose hasthe most useful functions as a hydrocolloid. Its extended conformationcauses the high viscosity of water-soluble starch and varies relativelylittle with temperature. The extended loosely helical chains possess arelatively hydrophobic inner surface that is not able to hold water welland more hydrophobic molecules such as lipids and aroma compounds caneasily replace this.

In order to obtain a starch-based odour control agent having a highspecific area, the agent material is preferably modified physically orphysicochemically.

Physical modifications concern mainly mechanical treatments such asgrinding and milling and sometimes heating. The treatment results inmodification at the surface leading to a slightly elevated surface area.

Physicochemical modification of starch granule is to allow them to swellin water, followed by dewatering. The process is conducted in such a(cautious) way that the granule remains intact. A sphere will ariseconsisting of holes and pores. Thus, physicochemical modification ofstarch, amylose and linear dextrin is a process in which the respectivesubstrates are treated in such a way that they will adopt a highspecific surface area, followed by a dewatering process to fixate thishigh surface area (see also example 8).

The starch-based odour control agents will work through basically twomechanisms: (1) (For a dry system) A malodour is adsorbed on a starch ora fraction thereof with an enhanced surface area. This can be achievedby swelling the starch, followed by exhaustive dewatering or drying (seee.g. example 3). (2) (For a wet system) The (hydrophobic) malodour isentrapped in the helix of amylose, especially V-amylose. In thiscontext, amylose will also apply to short chain amylose, i.e. lineardextrins.

V-amylose is a type of amylose. V-amylose has a hydrophobic inside ofits helix (suitable for a wet system). This configuration has theadvantage that it can adsorb hydrophobic substances to a high degree.V-amylose has a specific area of 20-200 m2/g (suitable for a drysystem).

Helical V-amylose (wherein the V stands for the German word“Verkleisterung”) will in its dry state adsorb due to its enhancedsurface area, whereas in the aqueous state it will adsorb due to theinclusion properties of hydrophobic substances. The properties inaqueous state can also be attributed to linear dextrins (small-sizedamylose). In the wet state, V-amylose is composed of very long helices(more than 10 turns) that can entrap the malodorous compound.

V-amylose is obtained from starch by fractionation. High amylomaizestarches are available from e.g. National starch; Hylon V (type Aaccording to table 1) and Hylon VII (type B according to table 1) having50 and 70% amylose (non-modified), respectively.

V-amylose will bind hydrophobic substances (for production of V-amylose,see the example section. Reference is also made to EP-A-648 116 and U.S.Pat. No. 3,881,991, which are included as references in this disclosure)in wet systems as well as in dry systems. Amylose, a linear polymerwhich is a fraction of starch has some special features. Its molecularweight varies, dependent on the source, between approximately 100000 and1000000 Da. At high temperatures it can be dissolved in water (>150°C.). When cooled to room temperature it starts to precipitate, a processknown as retrogradation. This is to be expected, because the amorphousform of amylose is not soluble in water. This process can be enhanced byaddition of various compounds, such as salts and water-miscible organicsolvents. Magnesium sulphate leads to precipitation of an amorphous formof amylose. Contrary to this a crystalline (highly ordered form) can beobtained by using organic solvents, which leads to formation ofinsoluble complexes in which the amylose has adopted a helicalconformation. Once freed from the complexing agent and dried, this formof amylose is cold-water soluble. In fact this structure is not quitestable, because during standing it will start to precipitate(retrograde). This process takes usually hours before any deposit isvisible. After standing for one day the precipitate is complete. Despitethis behaviour it is easy to isolate amylose with this conformationintact. An interesting feature is that the material is porous and has ahigh specific surface area. Because of the high specific surface (20g/m²-200 g/m²) it is expected to bind vapours from relatively volatilematerials. Details about isolation of the amylose fraction from starchcan be found in Adv. Carbohydrate Chemistry, 16, 299 (1961), or fromexample 1.

V-amylose dissolved in water can adopt a helical configuration andespecially in the presence of organic hydrophobic substances thisproperty is enhanced. Probably the helix is induced by the hydrophobiccompound because amylose adopts this configuration in which the innerside of the helix participates in hydrophobic interactions and the outerside, with its polar OH-groups, is directed to the water. In fact onecan state that in the presence of a hydrophobic substance amylose coilsitself round the hydrophobic substance.

The different types of amylose have very different properties (seetable).

TABLE 1 Survey of properties of different types of amylose Type ProcessSolubility in water Specific surface area A/B Salt Poor (<0.1 g/100 ml)Low (<1 m²/g) V Organic Good (>1 g/100 ml) High (20-200 m²/g)

The complex-forming properties differ between different amylose types.A/B-type will only form simple complexes on its surface. However, theV-type will dissolve and can form complexes also inside its structure.

Thus, amylose (especially the V-type) can be envisaged as an odourcontrol agent:

In dry state the amylose will bind (organic) vapours. This property isknown for substances with a relatively large specific surface area, e.g.carbon black. If amylose is located around the wet zone of a hygieneproduct, it will trap malodours originating from the liquid. However, ifamylose becomes wetted, it will dissolve and owing to its ability toform complexes with hydrophobic materials, it will continue to trapmalodours. These properties make amylose suitable as a unique odourcontrol material, both in dry and in wet phase.

Examples of substances that can bind to amylose are e.g. 3- and2-methylbutanal, amines, tetrahydrofuran, isovaleric acid,dimethylsulphide, octenone and octenol. These substances are veryimportant as such with respect to odours occurring in secretions.

Activated starch can be moisture sensitive, since water-molecules tendto bind to the surface thereby occupying binding sites. It does not havea hydrophobic part (in contrast to amylose), but a high specific surfacearea.

Normal starch is a spherical granule with a mean diameter of 1-100 μm,relatively dense (1.5). The actual sizes and distribution depend on thesource. The limited surface area (0-0.1 m2/g) reflects the fact thatabsorption and adsorption phenomena only play a limited role. Byswelling the granule, followed by dewatering a particle arises with amuch lower density and in which numerous pores are present. Thismaterial is much more active in the aspect of adsorption. Because thisproperty is enhanced we call the starch thus obtained active oractivated starch and the process to achieve this activation of starch.

Upon exposure to humid air, activated starch loses gradually its highspecific surface area. However, this process is occurring only slowly.

Linear dextrin has a specific surface area of 10-60 m²/g. It is producedfrom amylopectin. The molecular weight is about 2000-10000. Lineardextrin is composed of 1,4-alpha-linked glucose units (likecyclodextrin). It comprises 6-7 units per turn and 2-7 turns. Basically,linear dextrin can be regarded as amylose molecules, but having ashorter chain. Linear dextrin forms a helix that can entrap hydrophobicmolecules (for production of linear dextrin, see the example section.The most convenient way to prepare linear dextrins is from the fractionamylopectin In principle we can use either a waxy variety or theamylopectin fraction of any starch. An alternative is to hydrolyzeamylase (Reference is also made to U.S. Pat. No. 3,881,991, which isincluded as a reference in this disclosure). Compared to cyclodextrin,linear dextrin has an advantage in that complex formation is moreflexible due to 6-7 glucose units per turn.

TABLE 2 Comparison of starch based odour control agents of theinvention. Activated starch V-amylose Linear dextrin Source StarchStarch Amylopectin or amylose Composition Amylopectin/ Amylose Shortchain amylose amylose Fraction Not applicable Amylose Amylopectin or Nota natural amylose existing fraction Not a natural existing fractionMolecular 100 mil. -/200′-1 100′-1 mil. 2000-10000 weight mil. Surface20-150 m2/g 20-200 m2/g 10-60 m2/g area Helical Uncertain, but Yes, >10turns Yes, 2-7 turns form likely (6-7 units per turn) Sensitivity Yes,like zeolite. No Will lose some to water activity in humid airAdsorption Organic Organic Hydrophobic of compounds compounds compounds(volatile) and Hydrophobic Both gas and water compounds liquid Both gasand liquid Mechanism Dry: high surface Dry: high Dry: high surface area,binding of surface area will bind organic volatile area will organicvapors compounds bind organic Wet: hydrophobic Wet: when vaporsinteractions, will exposed to Wet: dissolves form a small helix humiditythe in water, surface area will hydrophobic decrease interactions, willform a helix Complex Moderate Good Good-moderate forming ability

The absorbent product can be any absorbent product in which odourcontrol is important for the use and comfort of the wearer, such asdiapers, sanitary napkins, pantiliners, incontinence garments and thelike.

The starch-based odour control agent of the invention can be applied tothe absorbent article in several different ways. What is important isthat it is applied so that it has the ability to prevent odours fromarising and/or prevent gaseous odours from spreading to the surroundingsof the absorbent product. The concentration that is applied for anevenly spread odour control agent, where it e.g. is glued to the backingsheet or on the material that is positioned closest to the skin, oralternatively on the wadding: 1-100 g/m2, preferably 1-50 g/m2, morepreferably 1-30 g/m2. The amount of odour control agent will varydepending on e.g. the type of agent and its capacity, as well as thetype and size of the product. The odour control agent can also bepositioned in the beard or in the belt on a belt product, or in thestanding gathers, so that the concentration is 1-200 g/m2, preferably1-50 g/m2. Also, the odour control agent can be zoned in specificallyexposed areas where the concentration of odour control agent may be ashigh as 2500 g/m2.

Further, as discussed above, linear dextrin and amylose are effective inboth wet and dry systems, whereas activated starch is more effective ina dry system. Hence, various starch-based odour control agents can becombined in order to provide an odour control system having theadvantages of both types of starch-based odour control agents. In apreferred embodiment linear dextrin and/or V-amylose, is applied topositions of the absorbent product where it will become wet; i.e. whereliquid will be stored or transported. Activated starch and/or V-amylose,(due to high specific area) is applied to positions of the absorbentproduct that will be kept dry, and where malodorous gases can betransported out of the product; such as the backing sheet, longitudinaland lateral edges of the product, positions of the top sheet that willnot become wet (i.e. not in the inlet zone) and other positions of theabsorbent product.

Moreover, the starch-based odour control agent can be applied to the topsheet, where it can be applied to the whole side of the top sheet facingthe wearer. It can also be applied in strings or in spots. Also, theagent can be mixed with the material of the top sheet, such as with thefibres of a nonwoven top sheet. Also, it can be applied on the side ofthe top sheet facing away from the wearer. Further, the odour controlagent can be applied to an underlying airlaid layer or acquisitionlayer, or it can be applied to the absorbent core. It is also possibleto apply the odour control agent to the backing sheet of the product, orto wings, standing gathers or longitudinal or lateral edges of theproduct, as long as it has the ability to be effective. The odourcontrol agent can also be applied to a combination of positions.Preferably, the odour control agent is applied to the absorbent coreand/or the inlet/acquisition layers or both.

The odour control agent can be applied within or on the material(s). Forexample, the odour control agent can be in the form of fibres havingodour controlling properties. Further, the odour control agent can besprinkled on a glue-coated surface. Also, the odour control agent can beplaced in the standing gathers or in the waist elastics (for instance byclamping it between two layers in a laminate). In case the odour controlagent is positioned in the waist elastics or leg elastics, it could beapplied to a separate strip, or be glued to a nonwoven material that isfolded to form a pocket, or it can be put in a foam structure, in theelastic thread, be coated on the fibres or on the backing sheet. Also,the odour control agent can be zoned to the parts where the malodoursare likely to be transported out from the absorbent product.

The starch-based odour control agent can also be combined with one ormore additional odour control agents, such as, acidic SAP, cyclodextrin,activated carbon, silica and/or zeolites. In a preferred embodiment thestarch-based odour control agent is combined with acidic SAP that ispositioned in the core.

The liquid-permeable top sheet is preferably made of a material showingproperties like dryness and softness at use of the absorbent product, asthis sheet lies against the body of the wearer. It is desired, that thesheet has a soft and textile-like surface, which remains dry also atrepeated wettings. The top sheet may for example be composed of nonwovenmaterial with a soft and smooth surface, such as for example a spunbondmade of polypropylene fibres. In order to keep the surface closest tothe skin of the wearer dry, a hydrophobic nonwoven-material may be used,which has holes, so that openings are formed in the material, whichopenings are greater than the cavities between the fibres of thematerial. In this way, fluid may be lead down through the holed openingsin the top sheet to the underlying absorption core. Other examples ofmaterial in the top sheet may for example be holed plastic films, suchas for example a holed polyethylene film. The top sheet may be connectedto the underlying backing sheet and to the absorption core by, forexample, glue or through some kind of thermal bonding.

The liquid-impermeable backing sheet consists of a flexible material,preferably a thin plastic film of PE (polyethylene), PP (polypropylene),a polyester, or some other kind of suitable material, such as ahydrophobic nonwoven-layer or a laminate of a thin film and a nonwovenmaterial. These types of laminates are often used in order to achieve asoft and a textile-like surface of the backing sheet. In order toaccomplish an airier and comfortable product it is also possible to usebreathable backing sheets, which prevents fluid from coming out of theabsorbent product, but that allows moisture to be ventilated. Thesebreathable backing sheets may be composed of single material layers, orof laminates of, for example, blown or moulded polyethylene films, whichhave been laminated with, for example, a nonwoven layer of spunbond orof spunbond-meltblown-spunbond (SMS).

The absorption body is typically built up by one or more layers ofcellulose fibres, for example cellulose fluff pulp. Other materials,which may be used, are for example absorbing nonwoven material, foammaterial, synthetic fibre materials or peat. In addition to cellulosefibres or other absorbing materials, the absorbent body may alsocomprise superabsorbent material, so called SAP (super absorbentpolymers), that is material in the form of fibres, particles, granula,film or the like, which material has the ability to absorb fluidcorresponding to several times the weight of the superabsorbentmaterial. The superabsorbent material binds the fluid and forms afluid-containing gel. Moreover, the absorbent body may comprise binders,form-stabilising components or the like. Additional layers improving theproperties may also be used, such as various types of fluid-spreadingmaterial layers or inserts, so called waddings. The absorbent body maybe chemically or physically treated in order to change the absorptionproperties. For instance, it is possible to provide an absorbent layerwith compressed regions and/or being compressed in the entire layer(s)in order to control the fluid flow in the absorbent body. It is alsopossible to enclose the absorbent layer(s) in an envelope of for exampletissue material.

Typically, the absorbent body has in its longitudinal direction anoutstretched form, and may for example be essentially rectangular,T-shaped or hourglass-shaped. An hourglass-shaped absorbent body iswider in the front and rear parts than in the crotch part, in order toprovide an efficient fluid absorption simultaneously as the designfacilitates the product to form and to close around the user, therebygiving a better fit around the legs.

In order to further prevent fluid or faeces to leak out, the absorbentproduct on the side that is facing the wearer may also be equipped withinner fluid barriers, which are attached in connection to thelongitudinal edges inside the outer barriers. Preferably, the innerbarriers are made of an essentially liquid-impermeable material, such asfor example a hydrophobic nonwoven or a plastic film, and are formed asa longitudinal path with a first edge being connected to the absorbentproduct and a second free edge, which is adapted for being in closecontact with the user at use of the absorbent product. The second edgeis equipped with one or more elastic elements, preferably an elasticthread, which in contracted state contracts the free edge, whereby anupstanding barrier is formed. The inner barrier may be designed as astrip of a single sheet, wherein the free edge is turned down in orderto enclose the elastic element to prevent direct contact of the elasticthread to the user. Alternatively, the barrier may be formed of twocombined layers, whereby the elastic thread is attached to the edge ofthe free end between the two layers. In this case, the inner layer ofthe barrier may be composed of an elongation of the top sheet and theouter layer of an essentially liquid-impermeable material, or the innerand outer layers of the barrier may be composed of one single materialstrip, which is folded around the elastic thread.

The rear and/or front parts of the product may also be equipped with aso called waist elastics, which is composed of elastic organs appliedalong the front and/or rear end edges in order to give the product asoft and flexible enclosure around the waist of the user. Suitably, theelastic organs are attached between the backing sheet and the top sheetwith glue or through welding, such as ultra-sonic welding. The elasticorgans may be composed of one or more elastic threads, which in astretched state are applied between the sheets, and thereby form thewaist elastics. Alternatively, the elastics may be applied between thesheets in an unstretched state, whereby both sheets instead are gatheredor wrinkled at application. Another typical variant of the elastics,which is suitable, is elastic foam material composed of a thin strip offor example polyurethane foam, which like the elastic threads can beapplied between the two sheets. Of course, it is also possible toposition the elastic organs for the waist elastics on the outside of thebacking sheet or on the inside of the top sheet.

Optionally, the absorbent product is equipped with barrier flaps (alsocalled “standing gathers”). The main purpose of the barrier flaps is toprevent leakage of fluid from the absorbent product. Therefore, it isimportant that they provide a good fit to the wearer of the diaper. Thebarrier flaps have a proximal edge, which is close to the absorbent bodyand a free distal edge, which contacts the body of the user to providethe fluid barrier and also includes the elastic means.

Preferably, the barrier flaps extend along the entire length of theabsorbent core, but that may in some cases not be necessary, as long asthey provide a secure prevention against leakage. The height of thebarrier flaps is preferably 10-50 mm, and both the proximal edge and thedistal edge could be joined to the top-sheet in the front and rear endsof the product.

The barrier flaps are kept upstanding by the elastic means, whichpreferably runs along the distal edge inside the fold of the top sheet,which forms the flaps. This elastic means may be of any kind that isconventional in the art, and which fits into the flap.

The absorbent product may comprise a fastening system. This fasteningsystem may be of any kind, which is suitable for the product, such as ahook and loop system, or a tape.

In yet another embodiment, the absorbent core is equipped with a wickinglayer, which wicking layer has the purpose to spread fluid towards thefront part of the absorbent structure. Moreover, the wicking layer doesnot necessarily need to cover the whole absorbent core, but shouldpreferably cover at least the part of the absorbent core being in thefront part of the casing, more preferably the part being in the frontand crotch parts of the casing, and most preferably the entire absorbentcore.

The wicking layer is of a moisture permeable material, preferably tissuepaper or a hydrophilic non-woven, and functions to disperse the fluid,i.e. urine, passing through the liquid permeable top sheet, preferablyin a direction towards the front part of the diaper. The wicking layercomprises small capillaries directing the fluid towards smallercapillaries, due to capillary forces.

EXAMPLES Example 1 Procedure for Fractionation of Starch General Remarks

1. This procedure can be used for different types of starch amongstothers wheat, corn and potato. The A- and B-type amyloses are found innative starch granules, whereas the V-type only can be prepared byspecial procedures (see below). The amylose as described in the presentinvention concerns mainly (in a preferred embodiment) the V-type.2. The starches mentioned contain 25% amylose (linear) and 75%amylopectin.3. The procedures given below are examples.

Fractionation Procedure

A. A suspension of 50 grams of starch in 1 litre aqueous magnesiumsulphate solution (20%) is heated in an autoclave at 160° C. during 15minutes. The resulting starch solution is cooled to 70° C. and themagnesium sulphate concentration is adjusted to 9.4% (w/w) andsubsequently further cooled to room temperature. During the coolingprocess amylose precipitates. The precipitated material is isolated bycentrifugation. The pellet is washed repeatedly with water until saltfree, then washed twice with ethanol and finally with ether and dried.The yield is 12 grams of amorphous amylose. The amylose thus obtainedcan be transformed into the V-type by dissolving the amylose in water at160° C. in the presence of a suitable complex forming agent, e.g.2-methyl-1-butanol, followed by cooling (the further procedure isdescribed in the example given below for the fractionation of starch bycomplex forming agents.B. (alternative a) (V-type amylose) A suspension of 50 grams of starchin 1 litre of water and 200 ml 2-methyl-2-butanol is heated at 100° C.to gelatinise the starch. Then the mixture is heated in an autoclaveduring 15 minutes at 155° C. Upon cooling the amylose complexprecipitates. By centrifugation, the amylose is separated from theamylopectin fraction, which is still in solution. The pellet is washedtwice with an aqueous solution containing the complex forming agent(2-methyl-2-butanol), twice with 96% ethanol and finally with absoluteethanol. The solid is dried carefully at slightly elevated temperaturein vacuum. The amylose (V-type) thus obtained has some propertiesrequired for odour adsorption in both dry and wet state.C. (alternative b) (V-type amylose) A suspension of 50 grams of starchin 1 litre of water and 25 ml 2-methyl-1-butanol is heated at 100° C. togelatinise the starch. Then the mixture is heated in an autoclave during15 minutes at 155° C. Upon cooling the amylose complex precipitates. Bycentrifugation, the amylose is separated from the amylopectin fraction,which is still in solution. The pellet is washed twice with an aqueoussolution containing 2-methyl-1-butanol at the same concentration, twicewith 96% ethanol and finally with absolute ethanol. The solid is driedcarefully at slightly elevated temperature in vacuum. The amylose(V-type) thus obtained has some properties required for odour adsorptionin both dry and wet state.

Example 2 Binding of Acetaldehyde and Dimethylsulphide to V-Amylose

When V-amylose is exposed to the saturated atmosphere of acetaldehyde(AcH, boiling point 20° C.) and dimethylsulphide (DMS, boiling point 36°C.), the respective compounds are bound to an extent of 100%. Thus, thematerial can retain its own weight and this is higher than withactivated starch. After exposing the charged amylose to air considerableamounts are released but even after one day 20% of AcH or DMS is stillretained on the amylose.

Example 3 Preparation of Activated Starch

In this example maize starch has been used (Cas no 9005-25-8) fromSigma, art no S4126.

The maize starch is mixed with water and ethanol in the ratios: 1 partstarch to 10 parts water/ethanol mixture, wherein ethanol is 20% of theliquid mixture. The entire mixture is poured into a heat-resistantvessel that is put in an oven, 100° C. for 24 hours. After 24 hours themixture is poured in an excess of methanol in order to wash away thewater that was present during preparation and stirred cautiously for 24hours. The methanol and the residues (water and ethanol) from thepreparation are filtered away. Thereafter the maize starch is “washed”yet another 24 hours with methanol.

The next step is to wash off the methanol since it may comprise waterand because methanol is toxic. This is performed by the synthesis withacetone (another alternative can be to use a nonpolar solvent such asn-pentane). After all washing steps the maize starch is dried in vacuumat room temperature.

Since the maize starch tend to form lumps at the synthesis it can bebeneficial to grind the sample after drying.

Results

The relatively smooth starch beads/granules have become more porousafter the activation.

Example 4 Preparation of Linear Dextrin

Waxy maize starch (>99% amylopectin) is gelatinised (at 80-100° C.) ordissolved in water (>155° C.). After cooling to the temperature mostsuitable for the specific enzyme used, the mixture is incubated with adebranching enzyme. Specific examples of enzymes are Pseudomonasisoamylase (Hayashibara) (specific conditions: pH: 5-6; Temp: 35-40° C.)and pullulanase Promozyme (NOVO) (specific conditions: pH: 5; Temp:55-58° C.) supplier Novozyme.

The reaction is allowed to proceed for about 24 hours. Then a solutionis obtained, which consists mainly of linear dextrins. Upon heating theenzyme (protein) flocculates and can be removed by filtration,centrifugation or decantation. The resulting solution is slowly cooledto room temperature (this process usually requires >8 hours). Uponstanding a precipitate is formed. After one day, the dextrins areisolated by centrifugation or filtration. The water adhering to thedextrins is removed by repeated washings with ethanol, followed bywashing with absolute alcohol and drying in vacuum. An alternativemethod to isolate the dextrins is spray drying as mentioned in theHayashibara patent (U.S. Pat. No. 3,622,460). This has to be conductedunder careful chosen conditions i.e. inlet temperature<100° C.

Alternative preparations of the crystalline form of the dextrins includeaddition of complex forming agents like aliphatic alcohols (preferablybutanol and higher). Use of complex forming agents makes that thecooling down after reaction is less critical.

Also the products obtained by spray drying are better (have a higherspecific surface area.).

The enzyme dosage is based upon the activity of the enzyme. Usually 20units per gram of starch are used (range between 3 and 100 units). (Oneunit is able to convert 1 μmol substrate per minute at optimumconditions).

Example 5 Specific Surface Area of Activated Starch Upon Exposure toHumid Air

TABLE 3 Specific surface area (m2/g) of native and activated starch uponexposure to humid air Relative Relative Relative Exposure humidityhumidity humidity time (days) 35% 52% 81% 0 122 122 122 3 110 88 25 10102 88 16 17 103 81 16 24 98 78 10

Footnote: Physicochemical modification of amylose consists of thefollowing steps:

Conversion of amylose from its random configuration in aqueous solutioninto a helical form works through interaction with e.g. a hydrophobicalcohol (preferably C4) or higher complexes of amylose and thehydrophobic compound, which are insoluble in water, in other words aprecipitate is formed. Dewatering the precipitated complex through awater-miscible solvent leads to fixation of the coil. It can also beunderstood by the following reasoning: replacement of water by thewater-miscible solvent, which acts a complex forming agent. Solventssuch as methanol, ethanol and propanol are despite their hydrophiliccharacter still able to form complexes provided their concentration ishigh enough (60, 40 and 30%, respectively). Hereby, the complex formingagent is changed. By repeating the process a few times the final resultis that amylose is present in a helical form without the presence ofwater, but instead a volatile organic solvent in which the amylose isnot soluble. By evaporation the solvent is removed. The amylose is in ahelical form.

The situation with linear dextrins is somewhat different. The dextrins,prepared from amylopectin by enzymatic hydrolysis are initially solublein water, but form upon standing a crystalline precipitate. So, there isno complex forming agent needed, contrary to the high molecular weightamylose. By careful dewatering the crystalline form with its specificproperties (helix, high specific surface area) can be isolated. A verysimple way to accomplish this step is spray drying, which is preferredform of drying. Details are given in the Hayashibara patent.

Activated starch with a specific surface area of 122 m2/g is exposed ina closed vessel to air of a known relative humidity. The loss ofspecific surface area is determined as a function of time. It followsfrom table 3 that the loss is slow (it takes days) and that under humidconditions, the starch still retains an appreciable amount of specificsurface area.

Example 6 Adsorption of Xylene and Butanone on Starch and Carbon Black

TABLE 5 Adsorption (g/100 g substrate) of xylene and butanone on starchand carbon black. Xylene butanone Exposure Native corn Activated Nativecorn Activated time starch corn starch Carbon starch corn starch Carbon(hours) 1 2 black 1 2 black 0 0 0 0 0 0 0 1 4 10 18 2 10 18 8 5 25 35 324 33 20 6 35 38 4 65 35 1 specific surface area <0.1 m²/g 2 specificsurface area 120 m²/g

1. An absorbent product, having a longitudinal and a lateral direction,comprising a back sheet, being distal from a body of a wearer in use ofthe product, and a top sheet, being proximal to the body of the wearerin use of the product, said product having a front part, a rear part anda crotch part lying between the front and rear parts, the productfurther comprising an absorbent structure, between the top sheet and theback sheet, extending longitudinally from the front part to the rearpart, and the product further comprises at least one starch-based odourcontrol agent, and wherein the starch-based odour control agent has aspecific area of at least 5 m²/g.
 2. The absorbent product according toclaim 1, wherein the starch-based odour control agent has beenphysically or physicochemically modified in order to obtain an enhancedspecific area.
 3. The absorbent product according to claim 2, whereinthe physicochemical modification comprises the steps of: (a) swellingthe starch-based odour control agent material in water, and (b)dewatering the material of step (a), in order to obtain a starch-basedodour control agent having an enhanced specific area.
 4. The absorbentproduct according to claim 2, wherein the physicochemical modificationcomprises the step of precipitating the starch-based odour control agentfrom solution with a complex forming agent.
 5. The absorbent productaccording to claim 2, wherein the physicochemical modification comprisesthe step of precipitating the starch-based odour control agent, eitherspontaneously or in the presence of a complex forming agent.
 6. Theabsorbent product according to claim 1, wherein the starch-based odourcontrol agent has the ability to form complexes in water.
 7. Theabsorbent product according to claim 1, wherein the starch-based odourcontrol agent is effective in both wet and dry conditions.
 8. Theabsorbent product according to claim 1, wherein the starch-based odourcontrol agent at least partly is amylose.
 9. The absorbent productaccording to claim 8, wherein the amylose at least partly is V-amylose.10. The absorbent product according to claim 1, wherein the starch-basedodour control agent at least partly is linear dextrin.
 11. The absorbentproduct according to claim 1, wherein the starch-based odour controlagent at least partly is activated starch.
 12. The absorbent productaccording to claim 8, hereby activated starch, linear dextrin oramylose, is positioned mainly in the dry parts of the absorbent product.13. The absorbent product according to claim 8, whereby activated starchand/or amylose, and/or linear dextrin is positioned at positions of theabsorbent product where air mainly tend to be pressed out of theproduct.
 14. The absorbent product according to claim 8, wherein lineardextrin and/or amylose, is positioned mainly in the wet parts of theproduct or in both the wet and dry parts of the product
 15. Theabsorbent product according to claim 1, wherein the odour control agentis a combination of amylose, V-amylose, activated starch and/or lineardextrin.
 16. The absorbent product according to claim 1, wherein inaddition to at least one starch-based odour control agent at least onefurther odour control agent is used, which is chosen from the groupcomprising: acidic SAP, cyclodextrin, activated carbon, silica andzeolites.
 17. The absorbent product according to claim 1, wherein theodour control agent is positioned on the top sheet and/or is positioneddirectly under the top sheet. 18-19. (canceled)
 20. The absorbentproduct according to claim 1, wherein the odour control agent ispositioned directly under the top sheet.
 21. The absorbent productaccording to claim 1, wherein the odour control agent is positioned inthe absorbent core of the product.
 22. The absorbent product accordingto claim 1, wherein the odour control agent is positioned in the edgesof the product.
 23. The absorbent product according to claim 1, whereinthe odour control agent is applied within the top sheet.
 24. Theabsorbent product according to claim 1, wherein the odour control agentis applied within or on the backing sheet of the product.
 25. A methodof making an absorbent product, the method comprising: modifying astarch-based odour control agent in order to obtain an enhanced specificarea of at least 5 m²/g; and positioning the odour control agent on thetop sheet and/or directly under the top sheet, and/or in the absorbentcore of the product, and/or in the edges of the product, and/or isapplied within the top sheet and/or is applied within or on the backingsheet of the product, or any other layer of the product.
 26. The methodof claim 25, wherein the modifying process comprises (a) swelling thestarch-based odour control agent material in water, and (b) dewateringthe material of step (a).
 27. The method of claim 25, wherein themodifying process comprises precipitating the starch-based odour controlagent from solution with a complex forming agent.